New Zealand-based Duke Engines LTD has introduced the world's
only commercial 4-stroke axial piston spark ignited engine, and was
showing it last week at Oshkosh.The engine is lightweight, small,
valveless, vibration-free, has very high power density, and runs on
most fuels, including kerosene/jet fuel. The Duke engine is a great
fit for aerospace applications, including ultralight, experimental
and UAV platforms. They have 2 prototype models operational; a
103hp model and a 180hp model The former engine weighs 101 lbs with
no gearbox required. The latter engine weighs 101 lbs and requires
a gearbox.

These Duke engines have negligible 1st order and 2nd order
vibrations. They deliver high thermodynamic efficiency and offer
complete fuel flexibility. The engines are far less complex than
traditional engines because they have only 3 sets of spark plugs,
injectors and ports for 5 cylinders with no valve train. The
current Duke engines are the 5th generation prototypes.

The aerodynamically friendly cylindrical shape, with output
shaft on center line, and low weight, makes it easy to install in
small cowlings. The direct drive option produces 0.7 hp/lb., and
the geared option produces over 1.0 hp/lb.

The Duke engines will again be tested in the U.S., and the
company says it is actively seeking development partners for their
marketing efforts in the U.S.